Abstract
Partially sintered mullite ceramics and mullite-alumina (MA) composites have been prepared by uniaxial pressing and conventional sintering in the temperature range 1570–1620 °C. The temperature dependence of Young’s modulus and damping is determined by impulse excitation from room temperature to 1400 °C. For the mullite ceramics the temperature dependence of Young’s modulus exhibits the typical behavior expected for the majority of oxide ceramics, i.e. a continuous decrease with increasing temperature which can be conveniently described by master curves. The damping curves are unspectacular, showing only the usual steep increase at high temperature. For the MA composites the temperature dependence of Young’s modulus exhibits an anomaly, viz. an increase from 800° to 900°C to a maximum at 1050–1100 °C, which is discussed in terms of two hypotheses from the literature (“glass phase hypothesis” and “phase transition hypothesis”), although the ultimate reason for this anomaly remains unclear.
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